A logistics company claims that the average delivery time for local parcels is 12 hours. A manager suspects that recent changes in the sorting process have altered this mean delivery time. A random sample of 10 parcels is monitored, and their delivery times in hours are recorded as follows:
11.5,12.8,12.2,11.9,13.1,12.4,11.7,12.6,13.3,12.5 11.5, \quad 12.8, \quad 12.2, \quad 11.9, \quad 13.1, \quad 12.4, \quad 11.7, \quad 12.6, \quad 13.3, \quad 12.5 11.5,12.8,12.2,11.9,13.1,12.4,11.7,12.6,13.3,12.5Carry out a hypothesis test at the 5% significance level to investigate whether the mean delivery time has changed. You may assume that delivery times are normally distributed with a standard deviation of 0.6 hours.
